This invention relates to a portable boring machine.
Line boring is an operation whereby two axially aligned holes are bored in a workpiece. Typically, line boring is used to bore holes in the mounting ears for the bucket of a backhoe, where the previous holes have become enlarged through wear. Weld is built up on the interior of the previous holes, and is then bored out to define the new holes.
A conventional line boring machine comprises a power unit, a boring bar, which carries a cutting tool, and a supporting structure for supporting the boring bar and holding the power unit against rotation. The supporting structure is independent of the workpiece. The boring bar is circular in cross section, except for a key slot, and is connected drivingly to the power unit by use of a key that engages the key slot. The boring bar is positioned in the existing holes in the workpiece with the aid of cones that are fitted on the boring bar and are used to center the boring bar in the holes. When the boring bar is in the proper position, the supporting structure is locked to prevent further movement of the boring bar transverse to its central axis, and the cones are removed.
A conventional line boring machine is subject to disadvantage, in that it is heavy, and cannot be considered to be portable. Therefore, use of the conventional line boring machine in the field is difficult and inconvenient. In addition, the requirement that the boring bar be keyed precludes the use of standard bar material. Moreover, adjustment of the position of the boring bar during set-up of the machine is accomplished with the aid of the supporting structure, which supports the boring bar at one end through the power unit and at its opposite end through a bearing, and consequently it is necessary to move the power unit in order to center and align the boring bar. This results in the set-up of the machine being difficult.